In recent years, there has been a growing interest in developing minute chemical and biological laboratories, analytical devices, and reactors known collectively as laboratories on chips. The ability to perform chemical and biochemical reactions in such devices offers many benefits including reduced reactant and media volumes for safety and economy, and improved performance from increased thermal and mass transfer. In such devices, a spatially defined and controlled environment permits precise flow of reactants through the network. The flow of a fluid from one part of the device to another, and the efficient mixing of fluids are tasks that are far from trivial. In a micro-scale device such as a laboratory on a chip, mixing of fluids is a particular challenge as flows are at very low Reynolds numbers, turbulence is not available to promote mixing, and the insertion of moving components into these devices is difficult.
Electrostatic forces have been used to move liquids around such devices. These forces usually induce only very low flow rates, require the use of high electrical potentials, and can often cause significant heating of the solution which may be inappropriate for the materials being used or the reactions to be performed. The use of electromagnetic forces offers a means for manipulating at least slightly conductive liquids in microfluidic devices and systems.
The application of electromagnetic forces to pump and/or confine fluids is not new. It is known that magnetohydrodynamic (MHD) systems are capable of converting electromagnetic energy into mechanical work in fluid media. To date, MHD systems have mostly been used to pump highly conducting fluids such as liquid metals and ionized gases, to study ionospheric/astrophysical plasmas, and to control magnetic fusion devices. Recently, however, MHD micro-pumps in silicon and in ceramic substrates have been constructed demonstrating the ability of such pumps to move liquids through microscale conduits. These efforts, however, have addressed individual pumping devices and have not provided an effective means for either the controlled movement of liquids through a microfluidic network or the efficient mixing of liquids in such microscale environments. Although it is envisioned that this invention will be mostly used in the context of minute devices, the concepts are not limited for small devices and can be applied for large devices as well.
Relevant publications, each of which are incorporated herein in their entirety, are identified as follows:
Bau, H. H., 2001, A Case for Magnetohydrodynamics, Proceedings of the 2001 ASME International Mechanical Engineering Congress and Exhibition, New York, N.Y. 2001, November 11-16. CD. Vol 2.
Bau, H. H., Zhong, J., and Yi, M., 2001, A Minute Magneto Hydro Dynamic (MHD) Mixer, Sensors and Actuators B, 79/2-3, 205-213.
Bau, H., H., Zhu, J., Qian, S., and Xiang, Y., 2003, A Magneto-Hydrodynamically Controlled Fluidic Network, Sensors and Actuators B, 88, 205-216
Bau. H., H., Zhu, J., Qian, S., Xiang, Y., 2002, A Magneto-Hydrodynamic Micro Fluidic Network, IMECE 2002-33559, Proceedings of IMECE'02, 2002 ASME International Mechanical Engineering Congress & Exposition, New Orleans, La., Nov. 17-22, 2002.
Jang, V., and Lee, S. S., 2000, Theoretical and Experimental Study of MHD (Magneto-hydrodynamic) Micropump, Sensors and Actuators A, 80, 84-89.
Lemoff, A. V., and Lee, A. P., 2000, An AC Magnetohydrodynamic Micropump, Sensors and Actuators B, 63, 178-185.
Lee, A. P. and Lemoff, A., V., Micromachined Magnetohydrodynamic Actuators and Sensors, U.S. Pat. No. 6,146,103.
Qian, S., Zhu, J., and Bau, H. H., 2002, A Stirrer for Magneto-Hydrodynamically Controlled Micro Fluidic Networks, Physics of Fluids, 14 (10): 3584-3592.
Yi, M., Qian, S., and Bau, H. H., A Magneto-hydrodynamic (MHD) Chaotic Stirrer, J. Fluid Mechanics, 468, 153-177.
Xiang, Y. and Bau, H. H., 2003, Complex Magneto Hydrodynamic, Low Reynolds Number Flows, Physical Review Letters E, 68, 016312-1-016312-11.
Zhong, J., Yi, M., and Bau, H. H., 2002, A Magneto Hydrodynamic Pump Fabricated with Low Temperature Co-fired Ceramic Tapes, Sensors and Actuators A: Physical, 96, 1, 59-66.